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Suppressing strain propagation in ultrahigh-Ni cathodes during fast charging via epitaxial entropy-assisted coating

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Chen Zhao at Kyushu University
Chen Zhao
Chuanwei Wang
Chuanwei Wang
Chuanwei Wang
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Xiang Liu at Beihang University
Xiang Liu
In-hui Hwang at Pohang University of Science and Technology
In-hui Hwang
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Abstract and Figures

Surface reconstruction and the associated severe strain propagation have long been reported as the major cause of cathode failure during fast charging and long-term cycling. Despite tremendous attempts, no known strategies can simultaneously address the electro-chemomechanical instability without sacrificing energy and power density. Here we report an epitaxial entropy-assisted coating strategy for ultrahigh-Ni LiNixCoyMn1−x−yO2 (x ≥ 0.9) cathodes via an oriented attachment-driven reaction between Wadsley–Roth phase-based oxides and the layered-oxide cathodes. The high anti-cracking and anti-corrosion tolerances as well as the fast ionic transport of the entropy-assisted surface effectively improved the fast charging/discharging capability, wide temperature tolerance and thermal stability of the ultrahigh-Ni cathodes. Comprehensive analysis from the primary and secondary particle level to the electrode level using multi-scale in situ synchrotron X-ray probes reveals greatly reduced lattice dislocations, anisotropic lattice strain and oxygen release as well as improved bulk/local structural stability, even when charging beyond the threshold state of charge (75%) of layered cathodes.
The design principle and structures of epitaxial entropy-assisted coating a, Schematic illustrations of the entropy-assisted surface design for ultrahigh-Ni cathodes. The oriented attachment-driven phase transformation under thermal equilibrium of Wadsley–Roth nanocrystals and layered structure can induce epitaxial entropy-assisted coating layer formation on the NCM surface, achieving good cathode anti-corrosion and anti-cracking tolerances with fast ion transportation. b, In situ HEXRD during heating of Ni90 (L), nano-Nb12WO33 (WR) and nano-ZrO2 (ZrO2) with equal weight ratio. Pink dashed boxes indicate pristine layer phase. White dashed boxes indicate emerging new peaks. c, HAADF–TEM and corresponding EDS element mappings of EEC–Ni90. d, High-resolution TEM image and fast Fourier transform patterns of selected region i (red) and ii (orange). The layer outside the EEC layer is Au for the purpose of protecting samples during focused ion beam TEM sample preparation.
The design principle and structures of epitaxial entropy-assisted coating a, Schematic illustrations of the entropy-assisted surface design for ultrahigh-Ni cathodes. The oriented attachment-driven phase transformation under thermal equilibrium of Wadsley–Roth nanocrystals and layered structure can induce epitaxial entropy-assisted coating layer formation on the NCM surface, achieving good cathode anti-corrosion and anti-cracking tolerances with fast ion transportation. b, In situ HEXRD during heating of Ni90 (L), nano-Nb12WO33 (WR) and nano-ZrO2 (ZrO2) with equal weight ratio. Pink dashed boxes indicate pristine layer phase. White dashed boxes indicate emerging new peaks. c, HAADF–TEM and corresponding EDS element mappings of EEC–Ni90. d, High-resolution TEM image and fast Fourier transform patterns of selected region i (red) and ii (orange). The layer outside the EEC layer is Au for the purpose of protecting samples during focused ion beam TEM sample preparation.
… 
Electrochemical and post mortem evaluations a, Cycling performance of bare Ni90 and EEC–Ni90 cathode at 1.0C. b, The corresponding voltage profiles of bare Ni90 and EEC–Ni90 cathode at 1.0C. c, Cycling performance of the bare Ni90 and EEC–Ni90 cathode at 2.0C. Hollow and solid symbols in a and c represent discharge specific capacity and Coulombic efficiency, respectively. d–g, Low- (d,f) and high- (e,g) magnification cross-section SEM images of cycled Ni90 (d,e) and EEC–Ni90 (f,g) cathodes after 500 cycles at 2.0C. h–k, ToF–SIMS secondary elements mapping (h,i) and depth profiles (j,k) of cycled Li metal anode after 500 cycles at 2C when coupling with Ni90 (h,j) and EEC–Ni90 (i,k) cathodes.
Electrochemical and post mortem evaluations a, Cycling performance of bare Ni90 and EEC–Ni90 cathode at 1.0C. b, The corresponding voltage profiles of bare Ni90 and EEC–Ni90 cathode at 1.0C. c, Cycling performance of the bare Ni90 and EEC–Ni90 cathode at 2.0C. Hollow and solid symbols in a and c represent discharge specific capacity and Coulombic efficiency, respectively. d–g, Low- (d,f) and high- (e,g) magnification cross-section SEM images of cycled Ni90 (d,e) and EEC–Ni90 (f,g) cathodes after 500 cycles at 2.0C. h–k, ToF–SIMS secondary elements mapping (h,i) and depth profiles (j,k) of cycled Li metal anode after 500 cycles at 2C when coupling with Ni90 (h,j) and EEC–Ni90 (i,k) cathodes.
… 
Bulk and local phase structure stability characterizations a–d, In situ HEXRD patterns of (003) peaks (a), c-lattice parameter (b), lattice volume (c) and c/a (d) changes of EEC–Ni90 and Ni90 cathodes during charge/discharge. e,f, In situ CMCD characterization of EEC–Ni90 cathode during charge/discharge: the voltage profiles (left) and azimuthal average (right) of (003) peak during the initial charge/discharge of EEC–Ni90 cathode at 0.3C (e) and selected CMCD patterns for the Debye–Scherrer ring of the (003) peak at open-circuit voltage (OCV), 4.19 V (charge), 4.28 V (charge) and 2.91 V (discharge) (f). The arrows indicate the (003) reflection positions of selected bright diffraction spots. d, d spacing of (003) peak. The direct beam is on the top side of the diffraction patterns.
Bulk and local phase structure stability characterizations a–d, In situ HEXRD patterns of (003) peaks (a), c-lattice parameter (b), lattice volume (c) and c/a (d) changes of EEC–Ni90 and Ni90 cathodes during charge/discharge. e,f, In situ CMCD characterization of EEC–Ni90 cathode during charge/discharge: the voltage profiles (left) and azimuthal average (right) of (003) peak during the initial charge/discharge of EEC–Ni90 cathode at 0.3C (e) and selected CMCD patterns for the Debye–Scherrer ring of the (003) peak at open-circuit voltage (OCV), 4.19 V (charge), 4.28 V (charge) and 2.91 V (discharge) (f). The arrows indicate the (003) reflection positions of selected bright diffraction spots. d, d spacing of (003) peak. The direct beam is on the top side of the diffraction patterns.
… 
Strain evaluation within the cathode particle through BCDI characterizations a,b, Three-dimensional isosurface rendering and cross-section atomic displacement field images of EEC–Ni90 (a) and Ni90 (b) cathodes after exposure to electrolytes for 30 h. c,d, In situ BCDI images of EEC–Ni90 cathode in the atomic displacement (c) and strain (d) field at different SoC.
Strain evaluation within the cathode particle through BCDI characterizations a,b, Three-dimensional isosurface rendering and cross-section atomic displacement field images of EEC–Ni90 (a) and Ni90 (b) cathodes after exposure to electrolytes for 30 h. c,d, In situ BCDI images of EEC–Ni90 cathode in the atomic displacement (c) and strain (d) field at different SoC.
… 
Local structure/environment analysis during operation a,b, In situ XANES contour (a) and in situ EXAFS contour (b) combined with the voltage profiles of EEC–Ni90 during the initial cycle. c,d, In situ XANES spectra combined with standard LiNiO2 (NiIII) and NiO (NiII) samples of EEC–Ni90 during initial charging process when 0 < SoC < 0.52 (c) and 0.56 < SoC < 0.94 (d). e, In situ EXAFS spectra of EEC–Ni90 during the initial cycle. f,g, In situ EXAFS fitting results of EEC–Ni90 during the initial cycle when 0 < SoC < 0.52 (f) and 0.56 < SoC < 0.94 (g). a.u., atomic units. h, The Ni–O1 bond length and Debye–Waller factor of EEC–Ni90 cathode as a function of SoC, collected from the fitting of corresponding EXAFS spectra with a sample size of 21. The error bar indicates the error range during EXAFS fitting. Source data
+1
Local structure/environment analysis during operation a,b, In situ XANES contour (a) and in situ EXAFS contour (b) combined with the voltage profiles of EEC–Ni90 during the initial cycle. c,d, In situ XANES spectra combined with standard LiNiO2 (NiIII) and NiO (NiII) samples of EEC–Ni90 during initial charging process when 0 < SoC < 0.52 (c) and 0.56 < SoC < 0.94 (d). e, In situ EXAFS spectra of EEC–Ni90 during the initial cycle. f,g, In situ EXAFS fitting results of EEC–Ni90 during the initial cycle when 0 < SoC < 0.52 (f) and 0.56 < SoC < 0.94 (g). a.u., atomic units. h, The Ni–O1 bond length and Debye–Waller factor of EEC–Ni90 cathode as a function of SoC, collected from the fitting of corresponding EXAFS spectra with a sample size of 21. The error bar indicates the error range during EXAFS fitting. Source data
… 
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Nature Energy | Volume 9 | March 2024 | 345–356 345
nature energy
https://doi.org/10.1038/s41560-024-01465-2
Article
Suppressing strain propagation in
ultrahigh-Ni cathodes during fast charging
via epitaxial entropy-assisted coating
Chen Zhao   1,9, Chuanwei Wang   2,9, Xiang Liu1, Inhui Hwang   3, Tianyi Li   3,
Xinwei Zhou4, Jiecheng Diao5,6, Junjing Deng   3, Yan Qin1, Zhenzhen Yang1,
Guanyi Wang4, Wenqian Xu   3, Chengjun Sun3, Longlong Wu   7, Wonsuk Cha3,
Ian Robinson   5,7, Ross Harder3, Yi Jiang   3, Tekin Bicer   3, Jun-Tao Li2,
Wenquan Lu   1, Luxi Li   3 , Yuzi Liu   4 , Shi-Gang Sun   8,
Gui-Liang Xu   1 & Khalil Amine   1
Surface reconstruction and the associated severe strain propagation
have long been reported as the major cause of cathode failure during fast
charging and long-term cycling. Despite tremendous attempts, no known
strategies can simultaneously address the electro-chemomechanical
instability without sacricing energy and power density. Here we
report an epitaxial entropy-assisted coating strategy for ultrahigh-Ni
LiNixCoyMn1−x−yO2 (x ≥ 0.9) cathodes via an oriented attachment-driven
reaction between Wadsley–Roth phase-based oxides and the layered-oxide
cathodes. The high anti-cracking and anti-corrosion tolerances as well as
the fast ionic transport of the entropy-assisted surface eectively improved
the fast charging/discharging capability, wide temperature tolerance and
thermal stability of the ultrahigh-Ni cathodes. Comprehensive analysis
from the primary and secondary particle level to the electrode level using
multi-scale in situ synchrotron X-ray probes reveals greatly reduced
lattice dislocations, anisotropic lattice strain and oxygen release as well as
improved bulk/local structural stability, even when charging beyond the
threshold state of charge (75%) of layered cathodes.
The high energy densities of Ni-rich layered oxides have made them
promising cathodes for next-generation battery system to meet the
ever-increasing energy demands of electric vehicles
1–3
. However, the
intrinsic high reactivity of highly delithiated Ni-rich cathodes with
electrolytes has led to a series of persistent structural fatigue issues
including the layered-to-spinel/rock salt phase transformation
4
and
lattice oxygen loss5 at the surface or in near-surface structures, which
deteriorate the cathode–electrolyte interphase (CEI) and increase
the cell impedance. The reconstructed surface often further blocks
the transport of lithium ions and electrons, leading to severe local
charge heterogeneity from the particles across the entire electrodes
6,7
.
Coupled with the inherent anisotropic lattice variation of layered
Received: 22 May 2023
Accepted: 17 January 2024
Published online: 29 February 2024
Check for updates
1Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL, USA. 2College of Energy, Xiamen University, Xiamen, China.
3X-ray Science Division, Argonne National Laboratory, Lemont, IL, USA. 4Center for Nanoscale Materials, Argonne National Laboratory, Lemont, IL, USA.
5London Centre for Nanotechnology, University College London, London, UK. 6Center for Transformative Science, ShanghaiTech University, Shanghai,
China. 7Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, USA. 8Collaborative Innovation Center
of Chemistry for Energy Materials, State Key Laboratory Physical Chemistry of Solid Surfaces, Department of Chemistry, Xiamen University, Xiamen,
China. 9These authors contributed equally: Chen Zhao, Chuanwei Wang. e-mail: luxili@anl.gov; yuziliu@anl.gov; xug@anl.gov; amine@anl.gov
Content courtesy of Springer Nature, terms of use apply. Rights reserved
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